The mammalian cerebral cortex is a complex structure that is responsible for our highest cognitive and perceptual abilities. The cerebral cortex is patterned into six layers, distinguishable by the density, morphology and wiring pattern of their constituent neurons. All cortical neurons are derived from progenitor cells in the proliferative ventricular zone, however, how the diverse neuronal phenotypes in the cortical plate could arise from the morphologically homogeneous proliferative zone is largely unknown. Using a recently generated antibody which labels only the deep layer (layers 5 and 6) neurons in the cortex, this proposal has designed cell culture experiments to elucidate the possible mechanisms by which the deep layer fate is determined during development. In particular, the nature of the environmental cues which may influence the cell fate decision of deep layer precursors will be examined. The proposed experiments may also set up a system for further in vitro experiments to study the laminar specification of cortical neurons when more layer specific markers become available.